1. Field of the Invention
This invention is in the field of electrical switching as controlled by the tilt angle of a switch body. It specifically concerns switches in which the moving element is a quantity of conductive liquid--normally metallic mercury. When the mercury has flowed to bridge an internal gap, because the switch is tilted appropriately, the switch conducts. In the untilted position switches of this sort are normally open.
2. Description of Prior Art
Most mercury tilt switches are built into an evacuated glass tube with electrodes penetrating the glass envelope. These switches have the advantages that they can be either normally-open or normally closed, and that fairly large currents can be handled by making the pool of mercury which moves bodily all at once-fairly large. They have several disadvantages also, a primary one being that they sense tilt only in one plane. Further, being glass they are inclined to break and so to contaminate their surroundings. Morrison in U.S. Pat. No. 2,713,159 shows a multidirectional mercury switch which makes contact between a base plate and a ring electrode. As shown his device requires quite a few parts with sealing contact between contact members and housing if the switch is to be sealed. It also depends on flow of the mercury over a surface, an effect I have found to be rather unreproducible and unreliable. Controlling the motion of mercury over surfaces is particularly hard when one is seeking to sense and react to small angles of tilt.